Dozens of dams found to put fish in danger

A screening of California’s more than 1,400 dams has found that 181 dams are potentially imperiling native fish downstream.

The study of the dams and rivers, conducted with tools developed at the Center for Watershed Sciences at UC Davis, seeks to identify where native fish and fish species are most endangered because of low or inconsistent river flows. A total of 753 large dams in California were evaluated in the study, whose results were published last week in the journal BioScience.

The study began in 2011, but its findings have been made more urgent by the drought, said Theodore Grantham, research biologist with the U.S. Geologic Survey.

About a quarter of the dams were identified as problematic, including Folsom, Trinity, New Melones and Pine Flat.

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The dams affecting the greatest number of native species with sensitive fish populations include the Keswick and Anderson-Cottonwood dams on the Sacramento River, and Woodbridge and Nash dams.

The inventory in the study does not include the many thousands of smaller dams in the state which are operated with little thought to their effect on fish, said Grantham, a co-author of the study.

Grantham said the goal of the study is to give dam operators, natural resource managers and policymakers the information needed to decide which dams need urgent attention to address potential harm to imperiled fish, including salmon and lampreys. A 2011 study found that 80 percent of California’s native fish are at risk of extinction if present trends continue.